arm64: dts: rockchip: Drop fephy pinctrl from gmac2phy on rk3328 rock-pi-e

Turns out the fephy pins are already claimed in the phy node, which is
rightfully where they should be claimed.

Drop the pinctrl properties from the gmac2phy node for the ROCK Pi E.

Fixes: b918e81f2145 ("arm64: dts: rockchip: rk3328: Add Radxa ROCK Pi E")
Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Link: https://lore.kernel.org/r/20210426095916.14574-1-wens@kernel.org
Signed-off-by: Heiko Stuebner <heiko@sntech.de>